%User Variables

\usetikzlibrary{calc,trees,positioning,arrows,chains,shapes.geometric}
\usetikzlibrary{decorations.pathreplacing,decorations.pathmorphing,shapes}
\usetikzlibrary{matrix,shapes.symbols,plotmarks,decorations.markings,shadows}

\newcommand{\block}{1cm}
\newcommand{\scale}{0.65}

\begin{tikzpicture}[scale=\scale,every node/.style={minimum size=0.6*\scale*\block}, inner sep=0pt,on grid]

    \definecolor{lightgray}{rgb}{0.80,0.80,0.80};
    \definecolor{darkgray}{rgb}{0.40,0.40,0.40};

    \tikzstyle{arrow}=[draw, <->,shorten <=1pt,shorten >=1pt,>=stealth',thick]
    \tikzstyle{pel}=[circle, rounded corners ,draw=lightgray, fill=lightgray, thick,  scale=0.5]


    % Neighbor pixels
    \foreach \x in {-2,...,10}
    \foreach \y in {-1,...,9}
    {
	  \node at (\x+0.5,\y+0.5) [pel]() {};
    }

    % 	\foreach \x in {0,8}
    % 	\foreach \y in {1,...,2,4,5,...,7}
    % 	{
    % 		\node at (\x+0.5,\y+0.5) [pel](ref_lft) {};
    % 	}


    % Center
    \draw[draw=black, dashed,thick, opacity=1]  (\block+4,\block+4) rectangle ++(7*\block-8,7*\block-8);
    \node[anchor=west,scale=\scale] at (1*\block+0.1*\block,8*\block+3) {Lost region ($R_L$)};


    % Lost pixel
    \node at (4*\block+\block/2, 3*\block+\block/2)
	  [pel, fill=black, draw=black, thick](lostpel)  [label=north east: $lp$] {};


    % Reference pixels
    \node at (4*\block+\block/2, 8*\block+\block/2)  [pel, fill=black, draw=black, thick](ref_tp)    [label=north west: $p_1$] {};
    \node at (0*\block+\block/2, 3*\block+\block/2)  [pel, fill=black, draw=black, thick](ref_lft)   [label=north west: $p_2$] {};
    \node at (4*\block+\block/2, 0*\block+\block/2)  [pel, fill=black, draw=black, thick](ref_bottm) [label=south east: $p_3$] {};
    \node at (8*\block+\block/2, 3*\block+\block/2)  [pel, fill=black, draw=black, thick](ref_rght)  [label=north east: $p_4$] {} ;

    \path [arrow] (lostpel) -- node[left]  { $d_1$} (ref_tp);
    \path [arrow] (lostpel) -- node[above] { $d_2$} (ref_lft);
    \path [arrow] (lostpel) -- node[left]  { $d_3$} (ref_bottm);
    \path [arrow] (lostpel) -- node[above] { $d_4$} (ref_rght);



    \node[anchor=west,scale=\scale] at (-1.4,10) (pixel_label) {Pixel};
    \node at (-1.5,8.4) (pel) {};
    \path [-latex,anchor=center] (pixel_label) edge (pel);

    \node[anchor=west,scale=\scale] at (5.8,6.0) (edge_label) {Contour};
    \path [-latex] (edge_label.south) edge (7.15,5.2);

    \node at (6.5,-1.3) (edge_start) {};
    \node at (10.3,8.1) (edge_end) {};
    \path [-,thick] (edge_start.north) edge[out=80, in=190] (edge_end.west);


\end{tikzpicture}